Major Depressive Disorder (MDD) places a staggering global burden on society. Of all mental disorders, MDD accounts for 4.4% of the total disability-adjusted life years (DALYs) lost and accounts for 11.9% of total years lost due to disability (YLD). With current trends, projection for the year 2020 is that depression will be second only to ischemic heart disease as the cause of DALYs lost worldwide.
A standard method of evaluating levels of MDD in patients includes such questionnaire-based assessment tools such as the 17-question Hamilton Depression Rating Scale (HAMD) and the Beck Depression Inventory (BDI), a 21-question multiple-choice self-report inventory. Both questionnaires result in a score of the patient, which is then translated into a clinical assessment by a physician. Although the HAMD and the BDI assessments are standard evaluation methods, there are well-known concerns about their validity and reliability.